ESA CCI Research Fellowship: Baptiste Vandecrux

Project: Water Under Snow Cover

Water Under Snow Cover: multi-frequency microwave observations of liquid water within Greenland ice sheet snow cover and its relation to runoff and supraglacial lakes

Fellowship project summary:

The Greenland ice sheet is a key component of the global climate system and its mass loss is one of the largest sources of contemporary global sea level rise. Each summer, a large part of the ice sheet surface undergoes surface melting. The water then infiltrates into the snow and either runs off from the ice sheet or refreezes. The fate of ice sheet meltwater is crucial for at least two Essential Climate Variables (ECV) monitored by ESA CCI: the total mass loss from the ice sheet, roughly half of which is meltwater runoff, and the summer extent of supraglacial lakes (SGL) that is a direct consequence of surrounding meltwater generation.

Although surface expression of the melt can be tracked from space from single-frequency microwave and optical remote sensing, the dynamics of the water under the surface is poorly documented. This project aims at detecting subsurface meltwater from multi-frequency microwave observations by combining microwave observations from multiple satellites (AMSR, SMOS, SSMI, SMAP, Sentinel-3) to in situ knowledge of subsurface water at the c. 40 PROMICE and GC-Net automatic weather stations (AWS): either detected from snow temperature measurements or simulated by an AWS data-driven snow model. A microwave emission model (SMRT) will be used to further understand the multi-frequency microwave observations from the ice sheet. The result is an estimation of the depth range to which each of these microwave frequencies are sensitive to and consequently, the construction of depth-resolved liquid water content (LWC) maps on the Greenland ice sheet.

Our LWC maps will indicate the depth of meltwater infiltration and the duration it remains liquid under the surface. These two variables will tightly constrain the surface melt intensity and subsurface meltwater refreezing which remain missing for remote and observation-based assessment of ice sheet melt and mass loss. The expected outcome will bring new depth of insight to the existing ECV, such as giving an upper boundary to the runoff area each melt season and delineating the catchment area feeding to the SGL. The output of this project can be used in combination with other EO dataset to gain insight in the ice sheet mass budget closure and to evaluate climate model estimates of the ice sheet mass loss.

Research fellow: Dr Baptiste Vandecrux

Host Institution: Geological Survey of Denmark and Greenland (GEUS)